Energia Geotermica: cos’è, come funziona e vantaggi

Geothermal energy: what it is, how it works and advantages

Used since ancient times, geothermal energy is one of the most widely used renewable sources in Italy and Europe. It exploits the Earth's heat and is present in quantities that could potentially meet the needs of humanity. Its advantages are many, but it is not always easy to organize its extraction. Let's see together everything there is to know about geothermal energy.

What is geothermal energy

Geothermal energy is a renewable energy source derived from the Earth's natural heat, which can be used for both electricity and thermal energy production. The natural heat of the Earth has been used since ancient times, especially in thermal sources - we have traces of it already in the Paleolithic and in China in the 3rd century BC - but its industrial exploitation started in Italy and more precisely in Larderello, in Tuscany, where already in 1827 they started to use the steam of a geyser to extract boric acid from a mud volcano. Even today Italy, thanks only to the Tuscan sites, is in eighth place in the global ranking for geothermal energy generation after the United States, Indonesia, Philippines, Turkey, Kenya, Mexico and New Zealand.

We have known since elementary school that the deeper you go into the Earth, the higher the temperatures of the subsurface, which increase by about 3 degrees every 100 meters. The rocks that are found in depth have a very high temperature and this causes the transformation into steam of groundwater that come into contact with them. This is the process that generates energy that can be used and exploited to produce electricity or heat.

Geothermal energy sources

The sources of geothermal energy are basically three:

  • Hydrothermal. These are those closest to the ground, located between 1 and 2 kilometers deep, and are among the most exploited by industrial systems. In fact, these are underground pockets of water heated by igneous rocks at high temperature and, depending on the dominant element, are divided in turn into dominant steam or dominant water sources.
  • Geopressurized. They are located between 2.5 and 10 kilometers deep and are true underground pockets that contain water at very high pressure and with a temperature that can reach 160 degrees. These geopressurized reservoirs can also contain large quantities of methane and for this reason they are ideal for the production not only of hydraulic energy, but also thermal energy.
  • Petrotermiche. They are found even deeper than the hydrothermal and geopressurized springs and for this reason are the most difficult to exploit. Here it is the same rocks, hotter because they are deeper, that are the source of energy. The problem, however, is the absence of water to turn into steam.

How to recover heat from the Earth

There are three main ways to recover heat from the Earth:

  • Classical (or high-enthalpy) geothermal energy.. The most effective and most widely used method. The temperature of the deposits in the subsoil exceeds 150° and water escapes in the form of geysers. The steam is channeled into the so-called "vapordotti" and directed towards the geothermal power plant, where it arrives by activating the turbines that, rotating, produce mechanical energy which is then transformed into electrical energy through the use of an alternator;
  • Medium enthalpy geothermal energy. The temperature of the deposits varies between 90° and 150°C. The Earth's heat is therefore lower and not enough to produce electricity directly. Therefore we need binary cycle power plants that can operate without the need for very high temperatures, but using fluids that evaporate at a lower temperature than water. Production in this case is not comparable to that of high-temperature plants, but these plants are more than sufficient to meet the needs of small local communities;
  • Low-enthalpy geothermal. Temperatures vary between 30° and 90° and this does not allow us to produce energy, but to exploit the heat to heat swimming pools, spas and even private homes thanks to geothermal heat pumps as an alternative to traditional boilers with a lower impact on the environment and a more efficient performance.

The advantages of geothermal energy

The advantages of geothermal energy are really many, for us and for the environment. Among the renewable energy sources, geothermal energy is the one that can produce the largest amount of electricity and this, already very important, is not the only advantage:

  • Although not inexhaustible, geothermal energy can be considered in all respects a renewable energy source because its production is equal to 100 billion times the annual world energy consumption. The heat that is extracted is really minimal compared to the heat contained and generated by the entire planet and this means that the extraction operations are not penalizing in terms of balance and sustainability;
  • Unlike other types of energy, geothermal energy is not subject to weather variations or to theday-night alternation;
  • Geothermal plants are silent and do not create acoustic problems and also respect the ecosystems present on planet earth. Not only that. The waste from the production of this type of energy can be recycled;
  • Geothermal plants, both domestic and industrial, have a very long average lifespan, even 80-100 years, and the absence of combustion not only averts the risk of fire, but also ensures excellent plant reliability. And, being closed-circuit systems, periodic maintenance is also very low.

And the disadvantages?

It's not all fun and games, but the disadvantages of geothermal energy are almost negligible compared to the enormous advantages. The first disadvantage is related to the first phase, that of the preliminary studies necessary to find the most suitable places to place the plants. It takes in-depth studies to identify the deposits that are often dispersed and are found at great depths, as well as expensive drilling to create the steam ducts to flow to the plants.

The bulk of geothermal power plants are located underground, but the parts that emerge risk visually disturbing the landscape. The good news is that more and more bio-architecture projects are aiming to integrate the installations into the natural environment and using non-polluting materials. Can we really consider this a disadvantage? Perhaps yes, at least in the immediate future, but it will no longer be so in the future.

And the same can be said of what is defined as another disadvantage: the sulfurous odor that geothermal power plants emit. Even in this case, however, abatement plants and filtering and containment systems can be implemented that minimize this risk.

In general, to contribute to the well-being of the planet, it is good to minimize energy consumption, using rechargeable products or products that reduce the weight of transport. Discover our rechargeable and low impact products on the R5 Living catalog.

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